Here's another installment of rationality quotes. The usual rules apply:
- Please post all quotes separately, so that they can be upvoted or downvoted separately. (If they are strongly related, reply to your own comments. If strongly ordered, then go ahead and post them together.)
- Do not quote yourself.
- Do not quote from Less Wrong itself, Overcoming Bias, or HPMoR.
- No more than 5 quotes per person per monthly thread, please.
I strongly disagree.
An old comment of mine gives us a counterexample. A couple of years ago, a meta-analysis of RCTs found that taking aspirin daily reduces the risk of dying from cancer by ~20% in middle-aged and older adults. This is very much a practically significant effect, and it's probably an underestimate for reasons I'll omit for brevity — look at the paper if you're curious.
If you do look at the paper, notice figure 1, which summarizes the results of the 8 individual RCTs the meta-analysis used. Even though all of the RCTs had sample sizes in the thousands, 7 of them failed to show a statistically significant effect, including the 4 largest (sample sizes 5139, 5085, 3711 & 3310). The effect is therefore "so small that a sample of several thousand is not sufficient to reliably observe it", but we would be absolutely wrong to infer that "it doesn't even matter that it is positive"!
The heuristic that a hard-to-detect effect is probably too small to care about is a fair rule of thumb, but it's only a heuristic. EHeller & Unnamed are quite right to point out that statistical significance and practical significance correlate only imperfectly.
That's a curious metric to choose. By that standard taking aspirin is about as healthy as playing a round of Russian Roulette.